Galium aparine is a herbaceous annual plant of the family Rubiaceae. It is native to North America and Eurasia. It has several common names, including Cleavers, Goosegrass, Stickywilly, Catchweed, and Coachweed.

The long stems of this climbing plant sprawl over the ground and other plants, reaching heights of 1-1.5 m, occasionally 2 m. The leaves are simple and borne in whorls of six to eight. Both leaves and stem have fine hairs tipped with tiny hooks. This makes them cling to clothes and fur much like velcro. The white to greenish flowers are small at 2-3 mm across, having four petals each.

It flowers in early spring to summer, with the flowers occurring in most of the leaf nodes. The fruits are burrs, produced in clusters 1-3 seeds; each seed is 4-6 mm diameter and covered with hooked hairs which cling to animal fur and clothing, aiding in seed dispersal.

It is abundant in hedges and other low shrubby vegetation, and is also a common weed in arable fields and gardens. As they grow quite rampantly and thickly, they end out shading out any small plants that they overrun.

The seeds are similar size to cereal grains, and thus are one of the most common contaminants in cereals since they are difficult to filter out. Their presence in cereals is not considered a serious problem as they are not toxic.